Acetabular dysplasia (a shallow hip socket) is a significant cause of osteoarthritis in young adults. The affected patients are usually unable to walk long distances, suffer from chronic pain, and usually limp. The major goals of osteotomy surgery are to 1) reduce patient pain and maintain his/her ability to perform normal daily physical activities, and 2) slow down or prevent the process of joint degeneration by reorienting the acetabulum to contain the femoral head and, therefore, reduce joint subluxation. In theory, both of these goals can be achieved by improving the contact pressure distribution on the acetabulum. Furthermore, one can hypothesize that reducing the maximum contact pressure of the acetabular cartilage will help to slow or prevent additional joint degeneration and reduce the incidence of osteoarthritis in dysplastic hips. PAO is inherently a challenging surgery performed only by a handful of surgeons in the United States. The few existing PAO navigation systems use optical system to track tools, and do not provide real-time tracking of the osteotomized fragment, 3D measurement of the realignment angles, and the osteotomy lines. Furthermore, surgeons use fluoroscopy to verify the joint realignment in the anterior-posterior plane only, limiting abilities to quantify the realignment of the joint in three-dimensional space. Our goal i to develop and evaluate a fluoroscopic guided system that performs three dimensional, real- time, intra-operative biomechanical analysis and fragment tracking to help surgeons improve the outcome of the periacetabular osteotomy (PAO). While the focus here is PAO surgery, applications of this research can be extended to other types of hip osteotomies, knee osteotomies, joint osteotomies, total hip replacement, and hip resurfacing techniques.